Embryology Of The GI Tract

Question 1

what is gastrulation ?

Answer 1

development of a trilaminar (mesoderm, ectoderm and endoderm) disc from a bilaminar disc

Question 2

what is the role of the mesentery ?

Answer 2

ventral and dorsal mesentery hang the gut tube from body wall and enclose organs

Question 3

how is the oesophagus developed ?

Answer 3

develops from the cranial aspect of the gut tube

lung bud develops at 4th week and the trachea-oesophageal septum separates these

Question 4

how does the stomach develop ?

Answer 4

foregut caudal to the oesophagus dilates to form the stomach (wk 4)

creates the greater and lesser curvatures

Question 5

what creates the lesser omentum ?

Answer 5

ventral mesentery

Question 6

what creates the greater omentum ?

Answer 6

dorsal mesentery

Question 7

how is the duodenum formed ?

Answer 7

formed from the caudal part of the foregut and cranial part of the midgut

(retroperitoneal)

Question 8

what liver apparatus is endodermal ?

Answer 8

hepatocytes, biliary epithelia, gallbladder, cystic duct

Question 9

what apparatus is mesodermal in origin in the liver ?

Answer 9

kupffer cells, haematopoietic, connective tissue, septum transverses

Question 10

how does the spleen develop ?

Answer 10

mesodermal at wk 5

T lymphocytes colonise at Wk 15-17

week 23 B cell precursors give spleen its lymphoid function

Question 11

what developmental anomaly’s can form in the foregut ?

Answer 11

oesophageal atresia or trachea-oesophageal fistula

obliterated bile duct

duplication of gallbladder

ventral pancreas which cuts off duodenum

Question 12

where does the midgut form from ?

Answer 12

opening of bile duct in the 2nd part of the duodenum to the proximal 2/3rds of transverse colon

Question 13

how is the primary intestinal loop formed ?

Answer 13

anticlockwise rotation causes physiological herniation of the loop at wk6

at week 10 the loop moves back into the abdominal cavity

vitelline duct connects the ileum and the yolk sac at 12-14 week

cecal bud develops at week 6

Question 14

what anomalies can be caused in the midgut ?

Answer 14

reversed or abnormal rotation

omphalocele

vitelline fistula/cyst/ligament/meckels

diverticulum

astresia/stenosis of intestinal loop

Question 15

what parts of the hindgut are endodermal in origin ?

Answer 15

distal 1/3rd of transverse colon, descending colon, sigmoid colon, rectum and upper anal canal

Question 16

what part of the hindgut Is ectodermal ?

Answer 16

lower part of the anal canal and anal orifice

Question 17

at what week can the cloacal membrane rupture ?

Answer 17

week 7

Question 18

what anomalies can form in the hindgut?

Answer 18

urorectal fistula
rectovaginal fistula
rectoperineal fistula
imperforated anus